Hi all, First post! Basically i have a Late 2009 iMac which i recently bought more RAM for, it originally had 2x 2gb chips in it which i have replaced with 2x 4gb Chips and all is good. Problems start when i try to add 2 more chips, i checked on the apple website and it said my iMac supports up to 16gb RAM so i went out and bought 4x 4gb Chips, Problem is when i put all 4 chips in, my iMac wont start up, it just beeps and the screen stays black. If i take 2 out, then it works with 8gb RAM. Ive tried all kinds of different combinations of different chips in different slots, it only ever works with 2 inserted. So my question is, am i trying to put more memory than it can handle in there or is there some special sequence, application or upgrade that i need to run in order to upgrade to 16gb? Thanks in advance for your help.